'London Whale' Sounded an Alarm on Risky Bets

The J.P. Morgan Chase & Co. trader known as the "London whale" tried to alert others at the bank to mounting risks months before his bets ballooned into more than $6 billion in losses, according to people familiar with emails reviewed by J.P. Morgan and a U.S. Senate panel.

The apparent reservations of Bruno Iksil, who earned the nickname after making outsize wagers in debt markets, are among the details being examined...